Feasibility study of radioimmunoguided iodine‐125 brachytherapy for metastatic colorectal cancer

The radioimmunoguided brachytherapy (RIGBY) approach was developed to identify and treat occult residual disease after resection. Between September 1989 and March 1992, 30 patients with metastatic recurrent colorectal cancer were implanted with iodine‐125 (¹²⁵I) seeds using the RIGBY technique. These patients would otherwise have died of disease progression. Patients were injected with ¹²⁵I radiolabeled antibody. A hand‐held gamma‐detecting probe (GDP) was used to detect and resect areas of high radioactivity representing tumor. Areas which had persistent high probe counts after resection represented areas of occult residual disease which were then implanted with a median dose of 160 Gy ¹²⁵I. The GDP was used to demarcate the occult tumor volume in 20 of 30 patients (67%). Patients were followed for 7–36 months (median 17 months); local control was 73% by clinical assessment; the median survival was 17.5 months, with 1‐year survival of 73% and 2‐year survival of 27%. There were no intraoperative deaths. Major surgical morbidity was seen in 9 patients (30%), comparable to the high morbidity seen in recurrent colorectal cancer patients undergoing major surgery. The RIGBY procedure did not significantly increase the morbidity. Further close follow‐up and additional accural of patients is warranted to evaluate the efficacy and morbidity of the RIGBY procedure, as well as evaluation of its other possible uses. © 1995 Wiley‐Liss, Inc.